3D-GIS spatial overlay analysis is being broadly concerned about in in ternational academe and is a research focus. It is one of the important function s of spatial analysis using GIS technology. An algorithm of multi-model spatial overlay based on three-dimensional terrain model TIN is introduced in this pape r which can be used to solve the TIN-based three-dimensional overlay operation in spatial analysis. The feasibility and validity of this algorithm is identified. This algorithm is used successfully in three-dimensional overlay and region va riation overlay analysis.